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Elizabeth Lewis PhD Dissertation.pdf (7.51 MB)

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Aging of Thin Glassy Polymers Probed by Ellipsometry and Mechanics

Lewis, Elizabeth A
http://rave.ohiolink.edu/etdc/view?acc_num=akron158465039485355

Abstract Details

2020, Doctor of Philosophy, University of Akron, Polymer Engineering.
The nature of interfacial interactions can significantly alter the physical and mechanical properties of thin polymer films. Glassy films are particularly prone to changes in physical aging in thin films, which can significantly alter the properties in applications. A glassy polymer film is initially inherently in a non-equilibrium state, but the chains will slowly relax towards equilibrium below the glass transition temperature (Tg). This aging can be assessed with a variety of properties from thermodynamic to volumetric to dynamic. In this work, the physical aging of a promising copolymer for membrane separations, butylnorbornene-ran-hydroxyhexafluoroisopropyl norbornene (BuNB-ran-HFANB), in thin films was systematically investigated. The BuNB-ran-HFANB film thickness and aging temperature both impacted the aging rate of the films. We observed rapid densification of the BuNB-ran-HFANB polymer even when aged >200°C below Tg via ellipsometric measurements during isothermal aging process. However, for the thinnest polymer films, the film thickness increases instead of decreases during aging, which we attribute to an initial highly non-equilibrium state for the BuNB-ran-HFANB chains as a result of the rapid evaporation during the spin coating process. The substrate selection for these films impacted the observed physical aging of the BuNB-ran-HFANB films with bare silicon, 2nm polystyrene sulfonate (PSS), and 2nm poly(acrylic acid) (PAA) coatings investigated as substrates for the BuNB-ran-HFANB films. The unusual aging behavior of increasing film thickness was seen for the thinnest polymer films for all three substrates, but the onset for the increasing thickness during aging was substrate dependent (<250nm for PSS, <115nm PAA, <150nm silicon). To understand this behavior, the stress state after different aging times were determined via wrinkling experiments on the aged films. The residual stress in the thin films initially increased during aging, but the stress then decreased approximately when the increase in film thickness occurred. These results suggest that the unusual aging behavior is associated with the stress state in the films.
Bryan Vogt (Advisor)
Kevin Cavicchi (Advisor)
Thein Kyu (Committee Chair)
Abraham Joy (Committee Member)
Jutta Luettmer-Strathmann (Committee Member)
182 p.
Polymer Chemistry; Polymers
Thin Films; Polymers; Ellipsometry, Mechanics; Polynorbornene; Physical Aging; Wrinkling

Recommended Citations

Citations

  • Lewis, E. A. (2020). Aging of Thin Glassy Polymers Probed by Ellipsometry and Mechanics [Doctoral dissertation, University of Akron]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=akron158465039485355

    APA Style (7th edition)

  • Lewis, Elizabeth. Aging of Thin Glassy Polymers Probed by Ellipsometry and Mechanics. 2020. University of Akron, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=akron158465039485355.

    MLA Style (8th edition)

  • Lewis, Elizabeth. "Aging of Thin Glassy Polymers Probed by Ellipsometry and Mechanics." Doctoral dissertation, University of Akron, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron158465039485355

    Chicago Manual of Style (17th edition)

akron158465039485355
414
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This open access ETD is published by University of Akron and OhioLINK.
Release 3.2.12